Gamma Rays

18 February, 2008

Gamma Rays lie at the far end of the electromagnetic spectrum. The most energetic form of light, Gamma Rays have the shortest wavelength. Electromagnetic radiation (light) has different properties depending on how much energy it has. This energy is directly related to the wavelength, so light with an extremely long wavelength (like Radio) does not have much energy in each photon. At the other end of the spectrum, gamma rays have very short wavelengths and a huge amount of energy in each and every photon. This energy can be very dangerous to living cells, and unlike the Hulk you are more likely to end up with cancer than super powers by being exposed to a lot of gamma radiation. In fact Gamma Rays are used to irradiate medical tools to ensure they have no leftover bacteria after an operation. Gamma Rays have limited uses on Earth, and we certainly wouldn’t want a mass explosion of them. In the late 1960’s, massive gamma ray bursts were detected which, if close enough, would wipe out all life on the planet.

In 1963 the Partial Test Ban Treaty came into effect. The Treaty banned setting off nuclear explosions in space, and the United States launched several satellites in order to monitor the Earth and watch for any illegal explosions. By the end of the decade they had not detected any radiation from the Earth’s atmosphere to suggest illegal weapons were being tested, but they had detected gamma rays coming from deep space. Later space missions also detected these bursts, but due to low resolution could not pinpoint where they came from. Just a decade ago, the BeppoSAX mission finally allowed scientists to discover the origin of these gamma ray bursts (GRBs). It was clear that these massive explosions were extra galactic in nature, and came from a long, long time ago. The current best accepted theory is that these GRBs are caused when an extremely massive, rapidly rotating star falls into a black hole. The energy released is immense.

If such a burst was to happen within 100 light years of the Earth it would blow the atmosphere away and melt the surface of the planet. Although only half of the Earth would be hit by the burst it would still manage to wipe out most, if not all, of life. Even at a several thousand light years away a GRB would cause mass extinction on the Earth. It is extremely unlikely that any such burst will occur near us, all of the really high energy GRBs occur far, far in the past, and possibly could only occur in the conditions of the early universe. Still, it would be a good idea to stay away from a star falling into a black hole. You wouldn’t like them when they’re angry.